1. Field of the Invention
The present invention relates to image processing, and more particularly, to an apparatus and method of encoding and decoding images.
2. Description of the Related Art
A conventional image encoding and decoding apparatus utilizes time-prediction encoding and decoding when encoding temporally successive images so as to remove redundant information between a previous image and a current image. In the time-prediction encoding and decoding method, the current image is subtracted from the previous image, and the subtracted result is encoded and decoded. According to H.264/MPEG-4 Part 10 AVC standardization suggested by the Joint Video Team (JVT) of ISO/IEC MPEG and ITU-T VCEG, there are various conventional time-prediction encoding and decoding methods (“Text of ISO/IEC FDIS 14496-10: Information Technology—Coding of audio-visual objects—Part 10: Advanced Video Coding”, ISO/IEC JTC 1/SC 29/WG 11, N5555, March, 2003). One of these methods is a weighted prediction encoding method in which prediction encoding is performed on a current image using the result of multiplying or adding a pixel value of a previous image by or to a constant value. This method provides excellent compression efficiency when applied to a region where images gradually become dark or bright or to a region in which two scenes overlap when one scene is replaced by another scene.
FIGS. 1A and 1B illustrate exemplary scene changing, in which FIG. 1A illustrates an example of scene changing occurring while two different scenes overlap, and FIG. 1B illustrates another example of scene changing using fade-out and fade-in.
Compression efficiency can be greatly increased using the weighted prediction encoding method when a scene changing, as illustrated FIGS. 1A and 1B, occurs. In the case of FIG. 1A, an intermediate image between a previous scene and a following scene can be weighted prediction-encoded by applying proper weight values to the previous and following scenes. In the case of FIG. 1B, a fading-out effect can be obtained by applying a proper weight value to the previous scene, and a fading-in effect can be obtained by applying a proper weight value to the following scene.
However, in the conventional method, the number of bits expressing a single pixel of an image is fixed at 8. Therefore, it is practically difficult to use the conventional method in the current circumstance where the need for high quality images continues to increase.